Queiroz has won several awards as a coach in junior levels, and has been successful at senior and club levels, mainly as Alex Ferguson's assistant manager. In 1998, he authored the Q-Report, which detailed plans to enhance football player development in the United States.

In 1984, Queiroz was appointed as assistant manager of Estoril-Praia. After that, Queiroz was appointed senior national team coach in 1991. He had a record of 14 wins in 31 matches.[5] Afterwards, he went on to manage the Portuguese SuperLiga team Sporting in 1994.

He subsequently coached the New York MetroStars in the United States and the Japanese team, Nagoya Grampus Eight. In between, he found time to author the "Q-Report", detailing plans to professionalize the development of football players in the United States. Queiroz returned to coaching national teams in 1999, when he took the job as coach of the United Arab Emirates, before becoming coach of South Africa in 2000. Under Queiroz, South Africa qualified for the 2002 FIFA World Cup, but Queiroz resigned before the finals after falling out with the South African Football Association.[citation needed]

Queiroz became a coach at English club Manchester United in June 2002. He began his work at the start of the 2002–03 season, working alongside Alex Ferguson, who had gone without an assistant manager since the departure of Steve McClaren in the middle of 2001.[6]

His position at Manchester United as assistant manager attracted the attention of Real Madrid, who wanted Queiroz as their manager to replace departing manager Vicente del Bosque in the summer of 2003. It was an opportunity to work with FIFA World Player of the Year award winners Zinedine Zidane, Ronaldo and Luís Figo; an opportunity which Queiroz was unable to turn down. He was appointed on a two-year contract, only a week after the arrival of Manchester United player David Beckham. Although Real Madrid were playing some of their best football in recent years, some argue that Queiroz failed at Madrid because of his tactical decisions (citation needed).

Real Madrid got off to a good start of the 2003–04 season, defeating Mallorca in the Spanish Supercup, and at mid-season the team topped the La Liga table and was in contention for the Spanish Cup and UEFA Champions League trophies. However, they went on to lose their final five matches and finished in 4th place, with Valencia winning the title. Real Madrid also disappointed in the Spanish Cup and Champions League, ending the season with Spanish Supercup as the only trophy won. Following 10 months at Real Madrid, Queiroz would join the long list of managerial failures at the Santiago Bernabéu Stadium, as he was sacked in May 2004.[7]

Reforming the old partnership with Alex Ferguson proved an attractive option to both sides. United had trailed 15 points behind Arsenal, and Ferguson was forced to bring in temporary help from Walter Smith during the tough end of season run-in. Subsequently, Queiroz returned to United as assistant manager on 1 July 2004, signing a three-year deal.

Queiroz was heavily rumoured[citation needed] to be one of the main reasons for team captainRoy Keane's departure from Manchester United in November 2005. According to Keane, he did not like the way Queiroz was given so much responsibility as if he were manager of the club and Keane did not like the tactics that Queiroz employed. One of the main outbursts of Keane's MUTV interview was aimed directly at Queiroz.

Queiroz was linked with managerial roles with Portuguese side Benfica[8] and the United States national team in 2006 but he remained with Manchester United to help them win the Premier League in 2007. Queiroz was often seen conducting interviews with BBC programmes, such as Match of the Day, as at the time Alex Ferguson refused to speak with the BBC after allegations by the BBC's Panorama programme that Ferguson's younger son Jason, and then Portsmouth manager Harry Redknapp, had been involved in corruption regarding cuts in transfer fees. Some of Queiroz's post-match opinions on refereeing were controversial. For example, in 2008 Queiroz was – unsuccessfully – charged with improper conduct by the Football Association after describing refereeMartin Atkinson's performance in a match as "a disgrace".[9][10]

In late March 2008, it was reported that Benfica had, once again, approached Queiroz to become their manager and had made a formal request to Manchester United.[11] United were heavily involved in the 2007–08 Premier League title race, five points clear at the top, with just seven games remaining, and also were still competing in the Champions League – being in the quarter-finals at the time of the enquiry. Queiroz did not make any public response to the approach.

Carlos Queiroz was brilliant. Just brilliant. Outstanding. An intelligent, meticulous man. He was good for me. He was a Rottweiler. He was the closest you could be to being the Manchester United manager without actually holding the title.

Following Benfica's approach, and amid rumors of an opening as the Portuguese national coach, Alex Ferguson started to push for Queiroz to be his successor as manager at Old Trafford and discouraged any possible suitors from approaching him.[13] However, rumours over the summer of 2008 continued to link Queiroz with the Portugal national team managers' role, following the departure of Luiz Felipe Scolari.[14] On 11 July 2008, Manchester United agreed to release Queiroz from his contract, and he was appointed manager for the Portuguese national team.

On 11 July 2008, it was announced that Queiroz was leaving Manchester United, having agreed to a four-year contract to become the head coach of the Portuguese national team.[15][16][17][18]

Portugal struggled under his management during the qualification for the World Cup 2010. Despite kick starting their World Cup Qualification campaign with a comfortable 4–0 win against Malta in Ta Qali', Queiroz's team failed to win any of their subsequent four matches.

Home form was poor, with a 3–2 defeat to Denmark followed by 0–0 draws against Albania and Sweden. Together with another goalless draw in Stockholm against Sweden, these results left Portugal with only 6 points out of a possible 15 and on the brink of missing a major international tournament for the first time since 1998. Building on an improving reliability in defence, Portugal defeated Albania in Tirana 2–1 with a late goal, tied 1–1 versus Denmark on 5 September, beat Hungary 1–0 and again 3–0 in the return match, and finally defeated Malta 4–0. These results, together with a defeat of Sweden to Denmark, enabled Portugal to finish the campaign second in the group with 19 points, one ahead of Sweden, and qualify for the UEFA play-off. They played Bosnia and Herzegovina in home and away legs. Portugal won 1–0 in Lisbon and followed up with a 1–0 victory in Zenica, Bosnia, and as a result they advanced to the finals of the 2010 FIFA World Cup.

At the World Cup, Portugal drew 0–0 with Côte d'Ivoire but then beat North Korea 7–0, the heaviest victory in the World Cup since Germany's 8–0 defeat of Saudi Arabia in 2002. This rout virtually guaranteed Portugal passage to the second round and a second goalless draw with Brazil confirmed qualification. In the second round they lost to Spain 1–0 and were knocked out having failed to score in three of their four World Cup matches.

Queiroz was sacked by the Portuguese Football Federation on 9 September 2010.[19] He was also suspended for six months by the Portuguese Anti-Doping Authority (Autoridade Antidopagem de Portugal) on 30 August.[20] On 23 March 2011, the Court of Arbitration for Sport upheld the appeal of Queiroz.[21]

In the opening match of the tournament on 16 June, Iran drew Nigeria 0–0, making it their first clean sheet of the FIFA World Cup.[28] In their next match, Iran was defeated by Argentina 1–0 with a late goal from Lionel Messi, and received praise after holding Argentina for 90 minutes while creating some attacking opportunities of their own.[29] Iran was eliminated from the tournament in their next game, a 3–1 defeat to Bosnia and Herzegovina. Iran's lone goal was scored by Reza Ghoochannejhad.[30] After the tournament, Queiroz extended his contract until the 2018 FIFA World Cup.[31]

Iran qualified for the 2015 AFC Asian Cup as group winners, where they were the highest ranked seed.[32] Iran faced Bahrain, Qatar, and the UAE in Group C.

With the second highest number of fans in the tournament after hosts Australia, the Iranians defeated Bahrain 2–0 with limited preparations.[33][34] A defensive minded Iran then defeated Qatar 1–0 thanks to a Sardar Azmoun goal before defeating the UAE by the same scoreline to reach the top of their group.[35][36]

Prior to the final 2014 World Cup qualification match against South Korea, Queiroz was angered by the comment made from Choi Kang-Hee, the coach of South Korea, who complained that Iran did not provide the training facilities with sufficient qualities during Korea's away qualification match against Iran on 17 October 2012. Choi stated that Korea would defeat Iran to help Uzbekistan qualify for the World Cup finals with Korea, and that Iran would have to watch the World Cup on television. The South Korean team also pledged to “make life painful” for Iran and to force their captain to cry “tears of blood”.[40] In response, Queiroz severely criticized Choi in his official comments and by wearing an affronting t-shirt.[41]

After Iran's victory against South Korea in their final qualification match, Queiroz showed his anger at the South Korean coach with a raised fist gesture which was deemed offensive by the Korean players and staff, almost causing a fight between the two teams.[42] As a result of the altercations, Sosha Makani was suspended for their opening match of the 2014 FIFA World Cup.[43] Queiroz had answered previously to Choi that Iran had fairly shared what they had with the Korean team on their visit to Iran.[44]

^At the time of Queiroz's tenure in the United States and Japan, the result of matches could not be a draw. In the event of scores being level at the end of 90 minutes, matches would be decided by extra time and penalties.